I read your letter on the nuclear testing problem with interest and sympathy. I can assure you that no decision I have taken in my Administration has given me more concern and sorrow than the decision to resume nuclear testing. It was a tragic choice; and I made it only because the alternative seemed to me to offer even greater dangers to or hopes for world peace, to unborn generations to come, and to the future of humanity.

If I had any assurance that the Soviet Union would not test again, I would never have directed that our tests be resumed. But it is impossible to believe that our refusal to test would have deterred the Soviet Union from initiation of a new test series whenever it suited their plans. The Soviet leaders have shown their contempt for world opinion in the past, and deference to this opinion is not likely to constrain them in the future. If the Soviet Union had been able to launch a new series without intervening tests on our part, it is conceivable that a grave shift in the world balance of power might have resulted, with fateful consequences for all our hopes for peace and freedom.

From the start of my Administration, I have tried to negotiate an agreement with the Soviet Union outlawing all nuclear tests. As you know, the Soviet Union has shown little interest in having such an agreement. Until the Soviet Union accepts a meaningful test ban agreement, I can see no choice, as the man responsible for the future of my country and my people, but to take necessary steps to protect the security position of the United States.

You raise the question of the need for international inspection. At present, national systems are able to detect seismic shocks but not reliably to identify them - i.e., they are not reliably able to distinguish an explosion from an earthquake. Until detection methods improve, there can be no alternative to some limited form of onside inspection. Obviously such inspection would apply to the United States and Great Britain as well as to the Soviet Union.

I need hardly say that, as the father of two children, I share your concern over the pernicious effect of radioactivity. I can only say that I had to weigh this against the alternative— that is, unlimited testing by the Soviet Union alone, leading to a steady increase in Soviet nuclear strength until the Communist world could be ready for a final offensive against the democracies. I believe that the Soviet leadership includes men genuinely devoted to the cause of peace. Our strength reinforces them in their arguments with their extremist colleagues. It would seriously underline their position if their country were permitted to acquire decisive nuclear superiority.

Nothing lies closer to my heart than the hope of bringing about general and complete disarmament under conditions of reliable international control. You are one of the transcendent moral influences of our century. I earnestly hope that you will consider throwing the great weight of that influence behind the movement for general and complete disarmament. I am happy to attach an outline of the basic provisions for such a treaty. I also enclose a study by our Arms Control and Disarmament Agency on 'The Detection and Identification of Underground Nuclear Explosions" and a copy of my speech of March 2 setting forth the considerations which led me to conclude in favor of the resumption of testing.